Citation and License

Genome Biology 2010, 11:R5
doi:10.1186/gb-2010-11-1-r5

Published: 13 January 2010

Abstract

Background

Radial chromosome positioning in interphase nuclei is nonrandom and can alter according
to developmental, differentiation, proliferation, or disease status. However, it is
not yet clear when and how chromosome repositioning is elicited.

Results

By investigating the positioning of all human chromosomes in primary fibroblasts that
have left the proliferative cell cycle, we have demonstrated that in cells made quiescent
by reversible growth arrest, chromosome positioning is altered considerably. We found
that with the removal of serum from the culture medium, chromosome repositioning took
less than 15 minutes, required energy and was inhibited by drugs affecting the polymerization
of myosin and actin. We also observed that when cells became quiescent, the nuclear
distribution of nuclear myosin 1β was dramatically different from that in proliferating
cells. If we suppressed the expression of nuclear myosin 1β by using RNA-interference
procedures, the movement of chromosomes after 15 minutes in low serum was inhibited.
When high serum was restored to the serum-starved cultures, chromosome repositioning
was evident only after 24 to 36 hours, and this coincided with a return to a proliferating
distribution of nuclear myosin 1β.

Conclusions

These findings demonstrate that genome organization in interphase nuclei is altered
considerably when cells leave the proliferative cell cycle and that repositioning
of chromosomes relies on efficient functioning of an active nuclear motor complex
that contains nuclear myosin 1β.